I think it is difficult to find a suitable chainwheel or rear sprocket for increasing speed for the CarryMe DS except you can find someone to CNC it or make it yourself. However, there's another way for increasing speed in the upper gear. You can just simply change the ATS speed-drive on your CarryMe DS to a Schlumpf High-speed-drive which gives you 2.5x of gear ratio instead of 1.65x given by the ATS speed-drive.